filial NDT Korean group in UAE & CIS
LRUT – LONG RANGE UT (EMAT
GW LRUT – Guided Wave Long Range Ultrasonic testing
Long Range Ultrasonic testing (LRUT) also known as Guided Wave Ultrasonic testing (GWUT) is an Ultrasonic method wherein ultrasonic waves are transmitted along the pipe wall (guiding walls) up to 180meters in length.
GW LRUT – Guided Wave Long Range Ultrasonic testing is a rapid screening test method for integrity assessment of pipelines, non-piggable buried, encased piping, vertical or inaccessible piping (e.g. overhead pipe racks) or epoxy coated pipelines to locate areas of potential degradation or engineering concerns and gross discontinuities for targeted assessment and inspection. While conventional NDT test methods provide localized inspection, underneath or in the vicinity of the sensors, LRUT is able to test 100% circumferential wall over tens of meters of the pipe length from the single inspection (contact point) location.
Guided Wave LRUT is used to inspect 100% of pipe circumference along the pipe length from a single location. Low frequency (15-85kHz) torsional or longitudinal guided waves are generated into the pipe body (360 degrees all around the pipe circumference) on both sides of the transducer assembly collar. These ultrasonic waves propagate in the axial direction of the pipe until the entire energy is attenuated or dissipated. When these guided waves intercepts areas of change in cross section such as butt welds, pipe supports, elbows, flanges or gross discontinuities such as severe corrosion, erosion, pitting clusters, etc; they reflect laminar waves back to the sensors at the location of wave initiation (Transducer assembly Collar). Multiple frequency signals are acquired simultaneously and analysed. The time-of-flight for each reflection and its dominant frequency is analysed to determine its location from the sensor. The quadrants determine the feature’s circumferential position on the pipe wall. The amplitude of the signal determines the significance of the defect in relative loss of cross section (LCS). The minimum LCS (loss of cross sectional area) that can be currently confidently detected is 3% of the total cross sectional area of the pipe under examination. One of the examples of representative cluster is shown in the following image.
Guided Wave LRUT is primarily applied on pipelines having limited access or only localised access; to avoid unnecessary excavation, coating removal or scaffolding installation. The use of LRUT significantly reduces maintenance costs and is a perfect inspection method for unpiggable pipes or inaccessible pipe sections. LRUT can be used on pipe diameters ranging from 38mm (1.5”) to 1200mm (48”) to detect loss of cross section (LSC) or areas of concern such as corrosion or erosion pockets around the pipe's circumference. The sensitivity of the LRUT is typically 2.5% LSC, equally sensitive on both ID and OD of the pipe. Absolute defect size will depend on the pipe size (for large ODs and wall thickness, 5% can be a penetrating defect). The signal amplitude will depend on the shape of a discontinuity e.g. extended area over the circumference or the extended depth in the wall. LRUT can be performed on in-service pipelines operating in the range of 0°C to 70°C. Testing can be done at higher temperatures and as low as -30°C but with exceptional risk management plans. Moreover, LRUT can be applied on various materials and different pipe diameters having wall thickness up to 40mm.
ASTM E2775 outlines a procedure for using GWUT on tubular carbon steel or low-alloy steel products having Nominal Pipe size (NPS) 2" to 48", and for wall thickness between 3.8 and 25.4 mm.
Typical scanning (interpretable) range from the single test location is the maximum ± 90 meters in each direction (180meters bidirectionally) for above ground or encased pipelines. The interpretation distance from the single location can be reduced by the following parameters.
Pipeline layout such as several bends, attachments, supports, branches & joints
Highly viscous liquid deposits on the internal or external pipewall.
Entire pipeline is severely corroded (Rapid attenuation of ultrasound and excessive noise reduces interpretable lengths of pipeline)
The type of coating e.g. Bitumin is a viscous liquid which dampens ultrasound.
Excessive thickness, diameter and the material of the pipeline
Generally, inspection range is set in relation to the defect size sought (sensitivity) and the attenuation of sound.
Ideal Applications:
Guided Wave Long Range Ultrasonic testing (GW LRUT) can be used for
Rapid inspection of in-service pipelines and piping for detecting corrosion or areas of concern (LCS)
Buried pipelines at the excavation locations or at level crossings
Encased (through-wall) pipelines or culvert line or PE coated pipes
Vertical pipes or structural circular columns
Inaccessible piping e.g. overhead piping rack
Requirement for high speed assessment to reduce cost reduction - Eliminate the cost of complete scaffolding or use of Elevated working platforms due to which testing speed is reduced.
Insulated pipelines and piping – No need to remove entire pipeline insulation
Detection of corrosion at pipe supports, clamps and pipe racks
Refinery, chemical plants, power station piping
Risers and offshore topside pipe work
Jetty lines and river crossing pipelines, tank farm link lines and sewer lines
Detection of Weld Root Erosion (See following image)
Advantages:
In-service inspection prevents production losses or downtime.
High productivity inspection - Reduction in onsite inspection time – maximum examination speed is 180meters per hour.
Examine 180meters (90m from each side of the transducers) from the single test location
Examine 100% of the pipe circumferential wall from the single test location (contact point)
Maintenance cost reduction by not removing
surface coating of the entire pipeline except 500mm width exposed to attach transducers.
insulation of the entire pipeline, except 500mm exposed to attach transducers.
No need to sand blast or grind entire pipeline surface under examination
No need to excavate the entire non-piggable pipeline or random spot tests
No need for a couplant which is necessary in conventional ultrasonics.
Detects weld root erosion faster than conventional test methods
Detects corrosion (loss of cross section
Limitations:
Guided Wave LRUT is a screening test method and hence precise measurement of minimum wall thickness (like PAUT) is not possible. After an area of concern is detected, average wall thickness measurements can be completed by Pulsed Eddy Current testing (PECT) as a faster technology. For precise wall thickness measurements, Phased Array Ultrasonic testing (PAUT) is recommended. For localised wall thickness measurement, conventional compression (longitudinal) wave ultrasonic testing can be applied.
Cannot detect an Isolated pit.
Testing of Cryogenic pipelines is possible but difficult – Exposed test location will condensate heavily and also the transducer may not detach from the frozen pipe wall surface.
Bitumin coated pipelines or buried pipes in contact with wet soil and wet silt or severely pitted pipelines attenuate sound severely and hence they are difficult to inspect.
100% surface area around the fillet weld cannot be assessed due to joint configurations.
Pipes less than 1.5inch diameter are currently not feasible to examine.
Minimum pipe length shall be 5meters for cost effective LRUT application.
Steel Pylons / Piles or pipeline under water = Approximately 15m minimum
Buried pipeline - dense clay embedded, Coal tar enamel coated in Victoria = 10m on each side of the Transducers
Expertise:
LRUT 2022d utilizes the latest technology LRUT instrument from NDT Korean Group, the UltraWave system. The UltraWave LRUT system is a higher resolution instrument as compared to some other technologies. One of the feature is having 1 kHz adjustable steps within a frequency spectrum of 15 to 85 kHz to evaluate signals better. As the GWUT is frequency dependent analysis, the software for this latest technology LRUT system is equipped with a unique F-scan color map that displays the entire frequency range acquired over the inspected pipe length. Olympus LRUT system also includes the active focusing capability to reduce signal-to-noise ratio which enhances flaw evaluation by delivering concentrated energy at a specific location on the pipe. The energy can be focused at eight different positions around the circumference, investigating the pipe cross-section, segment by segment. This active focusing estimates the circumferential extent of the indication by displaying a Polar graph.
LRUT 2022d system is a portable back-pack carry on system (8kg), battery operated which can performed by a single person.
Compared to conventional ultrasonic testing, Guided Wave LRUT instrument, transducers and software are complex and thus expensive. This test method requires highly trained, skilled and experienced personnel. LRUT 2022d must have trained, certified and experienced engineers to provide Guided Wave Long Range Ultrasonic testing (GW LRUT).
LRUT provides long-range inspections of pipes covering up to 100m per side (200m total). It uses the same instrument and complements MRUT for inspection of pipes at any distance.
For pipe and tube inspection using guided Wave
Portable EMAT inspection system (elbow also available
The system is capable of inspecting pipes at a speed of 60 cm per second with a real-time display.
The encoder is attached so that the location can be accurately identified.
The system can inspect pipes of all diameters and even plates by simply changing the sensor.
The photo above shows 2" and 3 " pipes and sensors.
Separate and detect fittings, cracks and corrosion conditions.
The lower part of the display above is from a round machined slot on the bottom.
Typical detection capacity is more than 10% corrosion, more than 10% crack, more than 20% fittings.
This device is intended to drive EMAT
Pulser / Receiver.
Use Win 95 or NT interfaces
The data can be analyzed.
Buy only hardware or software
It is also possible.
EMAT stands for Electro-Magnetic Acoustic Transducer, which is a metal with electromagnetic force
Means coupling to the sample. Therefore, EMAT does not have to contact the metal sample.
EMAT is a non-contact inspection method. The part where EMAT is applied can be divided into two major types
This is the case with non-ferrous metals and magnetic metals. In the case of magnetic metal, greater force can be obtained.
The figure below shows the principles of EMAT.
Measuring defects using EMAT is similar to using conventional piezoelectric devices.
Ultrasound is always ultrasound, and only the way the sensor is driven has changed.
But EMAT has a lot of vantage points because it can use several waveform modes
There are. That is, various waveform modes such as surface waves and plate waves can be generated and analyzed.
EMAT's high resolution and straight line responsiveness enable stress measurement.
EMAT can be used to easily measure material properties, such as residual stress, metal tissue(grain), and
Analysis of properties is possible.
The surface wave polarized in the horizontal direction proceeds in the vertical direction of the pole.
The progress of the wave in both directions provides useful information for measuring/analyzing the physical properties.
